The surfaces of kelp are covered with bacteria that may utilize kelp-produced carbon
and thereby contribute significantly to the carbon flux in kelp forest ecosystems. There is scant
knowledge about the identity of these bacteria and about which kelp-derived carbon sources they
utilize. An enrichment approach, using kelp constituent carbon sources for bacterial cultivation, was
used to identify bacterial populations associated with the kelp Laminaria hyperborea that degrade
kelp components. In order to assess whether the cultured bacteria are significant under natural conditions,
partial 16 rRNA gene sequences from the cultured bacteria were compared to sequences
obtained from the indigenous bacterial communities inhabiting natural kelp surface biofilms. The
results identify different members of the Roseobacter clade of Alphaproteobacteria in addition to
members of Gammaproteobacteria that are involved in kelp constituent degradation. These bacteria
are observed sporadically on natural kelp surfaces and may represent opportunistic bacteria important
in degradation of dead kelp material. Many of the cultured bacteria appear to be generalists
that are able to utilize different kelp carbon sources. This study is the first to link culturable kelpassociated
bacteria with their occurrence and possible roles in the natural environment.